The invention relates generally to the field of multiple-disc clutch packs, specifically clutch packs utilizing Magneto-rheological (MR) and Electro-Rheological (ER) substances.
ER and MR fluids and powders are substances that rely on a magnetic capable media compounded in a way that allows the substance to change form from a liquid or powder state to a rigid, solid state. These materials comprise micron-sized, magnetizable particles called fines, suspended in oil or other media. ER and MR powders consist solely of unsuspended magnetizable particles.
ER and MR fluids are similar in their operation. The main difference is that ER fluids are responsive to an electric field and MR fluids are reactive to a magnetic field. However, MR fluids do have some advantages over ER fluids.
In their liquid form, ER and MR fluids have a viscosity and consistency much like common motor oil. However, when an electric charge or magnetic field is applied, the fluids change form, becoming rigid and able to bond surfaces together. This rigid bonding mechanism results from a dipole moment introduced on the magnetic particles in the fluid from the electric charge or magnetic field. The particles form chains, aligning parallel to the electric charge or magnetic field. The strength of the bonding mechanism depends on the strength of the charge or field applied to the fluid and the size of the particles. The change in viscosity of the fluid takes place in a few milliseconds. ER and MR powders operate in the same manner, changing from a powder to a rigid form. MR fluids typically exhibit much stronger yield strengths than do ER fluids. MR fluids are also more resistant to temperature changes and have a high tolerance to impurities such as water. MR fluids can also be activated using a much lower voltage power supply. ER fluids require high voltage (near 5,000 volts) to operate. For purposes of the present disclosure, discussion herein of the terms xe2x80x9cER and/or MR fluidsxe2x80x9d is also meant to refer to equivalent ER or MR substances, such as powders.
ER and MR fluids have been examined in the past as a way to xe2x80x9clock upxe2x80x9d or stop a rotating device such as clutch plates. U.S. Pat. No. 2,575,360 describes such an application. The binding properties of the ER or MR fluid could increase the friction between two clutch plates quickly and easily, without having to actually change the axial displacement of the clutch plates. Instead of pressing the clutch plates against each other to bind them together, the ER or MR fluid could simply be activated and the solid form would bind the plates together.
A problem with using ER and MR fluids in this manner is that the fluid disperses during operation of the clutch due to centrifugation of the fluid outwardly and the random non-uniform gap thickness that can exist with flat surface disc clutch plates. When the fluid disperses, the binding properties of the fluid decrease and the clutch will lose its functionality. To solve this problem, it is necessary to replenish the fluid between the clutch plates. Pumping more fluid into the area between the clutch plates though holes in the adjoining shaft can accomplish this, but the plates must be moved apart in order to replenish the layer of fluid between them. This also necessitates a constant high energy power supply on the clutch mechanism to pump the fluid layer between the plates. It is desirable to keep a small volume of the fluid layer in place at all times, with the assistance of a residual low energy power supply, so that operation can be instantaneous, rather than having to replenish the fluid layer to maintain the functionality of the clutch pack. Or, in the alternative, it is desirable to have a mechanism to replenish the fluid layer without axially moving the plates.
In one embodiment of the present invention, a multiple-disc clutch pack is provided. The clutch pack comprises a plurality of porous metal plates mounted concentrically and each having a first and a second surface with at least one of the surfaces impregnated with a magneto-rheological substance. A plurality of grooves is defined on at least one of the surfaces of at least one of the plates.
In a second embodiment of the present invention, a multiple-disc clutch pack is provided. The clutch pack comprises a plurality of porous metal plates mounted concentrically and each having a first and a second surface with at least one of the surfaces impregnated with an electro-rheological substance. A plurality of grooves is defined on at least one of the surfaces of at least one of the plates.
In a third embodiment of the present invention, a multiple-disc clutch pack is provided. The clutch pack comprises at least one first porous metal plate having at least one substantially flat surface and at least one surface impregnated with a magneto-rheological substance. The invention further comprises at least one second porous metal plate having at least one waved surface and at least one surface impregnated with a magneto-rheological substance. The first and second plates are mounted concentrically such that the flat surface of the first plate faces the waved surface of the second plate.
In a fourth embodiment of the present invention, a multiple-disc clutch pack is provided. The clutch pack comprises at least one first porous metal plate having at least one substantially flat surface and at least one surface impregnated with an electro-rheological substance. The invention further comprises at least one second porous metal plate having at least one waved surface and at least one surface impregnated with a magneto-rheological substance. The first and second plates are mounted concentrically such that the flat surface of the first plate faces the waved surface of the second plate.
In a fifth embodiment of the present invention, a method for improving the functionality of a magneto-rheological substance in a multiple-disc clutch pack is provided comprising the steps of providing at least one first porous metal plate, providing at least one second porous metal plate and defining a plurality of grooves in at least one side of each metal plate. The method further comprises the steps of impregnating at least one side of each plate with a magneto-rheological substance and arranging the plates concentrically such that each grooved side of each plate faces non-grooved side of an adjacent plate.
In a sixth embodiment of the present invention, a method for improving the functionality of a magneto-rheological substance in a multiple-disc clutch pack is provided comprising the steps of providing at least one first porous metal plate with at least one substantially flat surface and impregnating the flat surface with a magneto-rheological substance. The method further comprises the steps of providing at least one second porous metal plate with at least one waved surface and impregnating the waved surface with a magneto-rheological substance and arranging the first and second plates concentrically such that each flat surface of each first plate faces a waved surface of a second plate.
In a seventh embodiment of the present invention, a method for improving the functionality of an electro-rheological substance in a multiple-disc clutch pack is provided comprising the steps of providing at least one first porous metal plate, providing at least one second porous metal plate and defining a plurality of grooves in at least one side of each metal plate. The method further comprises the steps of impregnating at least one side of each plate with an electro-rheological substance and arranging the plates concentrically such that each grooved side of each plate faces a non-grooved side of an adjacent plate.
In an eighth embodiment of the present invention, a method for improving the functionality of an electro-rheological substance in a multiple-disc clutch pack is provided comprising the steps of providing at least one first porous metal plate with at least one substantially flat surface and impregnating the flat surface with an electro-rheological substance. The method further comprises the steps of providing at least one second porous metal plate with at least one waved surface and impregnating the waved surface with an electro-rheological substance and arranging the first and second plates concentrically such that each flat surface of each first plate faces a waved surface of a second plate.